Organische Synthesen mit übergangsmetall‐Komplexen, 51. 1‐Metalla‐1,3,5‐triene und 1‐Metalla‐1,3‐dien‐5‐ine von Chrom und Wolfram durch Insertion von Alkinen in MC‐ bzw. CC‐Bindungen von 1‐Metalla‐1,3‐dienen bzw. 1‐Metalla‐1‐en‐2‐inen

Organic Syntheses via Transition Metal Complexes, 51. – 1‐Metalla‐1,3,5‐trienes and 1‐Metalla‐1,3‐dien‐5‐ynes of Chromium and Tungsten by Insertion of Alkynes into MC and CC Bonds of 1‐Metalla‐1,3‐dienes and 1‐Metalla‐1‐en‐3‐ynes, respectively 1‐Metalla‐1,3,5‐trienes L n MC(NEt 2 )–C(Me)C(OEt)–CHCHPh (3,4) and L n MC(OEt)– CHC(NEt 2 ) – C(Me)=CHPh [ 5 , L n MCr(CO) 5 ( a ), W(CO) 5 ( b )] are obtained for the first time from the corresponding 1‐metalla‐1,3‐dienes L n MC(OEt) – CHCHPh ( 1a, b ) under very mild conditions by the insertion of the electron‐rich alkyne Et 2 N–C C – Me ( 2 ) into the MC and the CC bonds, respectively, of 1 . The chelate complex ( 6b ) and the cyclobutenyl carbene complex 7b are isolated as minor side products. 1‐Metalla‐1,3‐dien‐5‐ynes L n MC(NEt 2 ) – C(Me)=C(OEt) – C CPh [ 9, 10 , L n MCr(CO) 5 ( a ), W(CO) 5 ( b )] are formed with high regio‐ and stereoselectivity on insertion of 2 into the MC bonds of 1‐metalla‐1‐en‐3‐ynes 8 . X‐ray data are given for the tungsten complex 3b .